The present invention relates in general to adjustable hand wrenches, variously known also as monkey wrenches, crescent wrenches or Stillson wrenches. More particularly, the present invention relates to an improvement in an adjustable wrench and particularly having to do with the ease and speed of adjustment of the adjustable wrench.
The typical adjustable wrench has a knurled worm gear which is rotated to make the adjustment by moving one jaw of the wrench. Ideally, this can be done by the thumb of the hand holding the wrench leaving the other hand free. However, often there is not sufficient room to accomplish the thumb movement necessary to make the adjustments. Because of the poor mechanical advantage of the knurled adjustment screw and the amount of movement necessary to make an adjustment, it is found that it is more reasonable to hold the wrench with one hand and make the adjustment with the other hand. Thus, the adjustment is a relatively time consuming process.
Another problem with the knurled screw adjustment device is that the direction of thumb movements relative to the hand is not constant; it reverses as the wrench faces left and right and also reverses as the wrench is held pointing up and pointing down. There is also interaction between the plains of rotation, as well as when the wrench is in an intermediate position within a plane, i.e., such as when the wrench points neither left nor right but perpendicular to the user. Accordingly, there is an unsureness on the part of the user as to which direction to move his thumb to open or close the wrench. This becomes additionally time consuming as the user engages in trial and error experimentation.
One type of an adjustable open end wrench is shown in U.S. Pat. No. 3,555,939. However, there are disadvantages associated with a type of wrench as shown in this patent. This prior art wrench contains relatively expensive components and is relatively complex to construct. Also, this prior art device is quite susceptible to malfunction due to dirt or metal pieces and requires a relatively smooth metal contact between certain components.
Accordingly, one object of the present invention is to provide an adjustable wrench having means for providing adjustment of the wrench by a relatively fast thrust of the thumb of the user.
Another object of the present invention is to provide an adjustable wrench which permits easy adjustment even in close quarters.
Still a further object of the present invention is to provide an adjustable wrench which has its adjustment movement always in a fixed direction, i.e., either toward or away from the wrench jaws.
Still another object of the present invention is to provide an adjustable wrench that is relatively simple in construction, uses relatively inexpensive parts, is easy to operate and also easy to clean.